Modern oven appliances are commonly equipped with a temperature sensor for determining the temperature inside the cooking chamber or oven cavity of the oven appliance. The temperature sensor is typically positioned on the rear wall near the top of the cooking chamber, although other locations have been used. A temperature display may also be provided whereby the user of the oven can monitor the temperature during cooking operations so as to properly cook a food placed into the oven.
The temperature sensor may also be used by e.g., a controller to operate heating elements inside the cooking chamber so as to achieve and then maintain a certain temperature in the cooking chamber according to one or more temperature set-points selected by the user. During cooking operations, the temperature in the cooking chamber can be affected by e.g., opening the oven door, the size and temperature of a food load placed into the oven, and heat losses to the environment. Thus, it is important to accurately measure and monitor the temperature in the cooking chamber throughout the cooking process.
The conventional placement of a temperature sensor at the top of the cooking chamber is problematic for several reasons. During operation of the appliance, a temperature gradient along the vertical direction of the cooking chamber can occur because, due to density differences, air at a higher temperature tends to rise to the top of the cooking chamber while air at a lower temperature tends to fall to the bottom of the cooking chamber. Because food is frequently placed at or near the vertical center of the oven chamber, the temperature of the air near the food can be quite different from the temperature measured by the temperature sensor. The temperature gradient problem can be further exacerbated while cooking in a mode where only a heating element along the top of the oven in close proximity to the temperature sensor is activated. Furthermore, regardless of position, radiant energy provided by one or more heating elements and reflected from the walls of the oven chamber can also adversely affect the accuracy of a temperature sensor placed in the cooking chamber.
It may be desirable to use other types of sensors during cooking operations to measure e.g., the humidity of air in the cooking chamber. However, because of the high temperatures (e.g., up to 500° F. during cooking, and over 800° F. during self-cleaning) that can be encountered in the cooking chamber, the use of such sensors may not be possible or practical. For example, such sensors may not be able to withstand such higher temperatures, direct exposure to IR radiation from the heating elements, or direct exposure to splattered substances e.g. grease or oil. Alternatively, the cost of providing more temperature resistant sensors may be prohibitive.